1. Field of the Invention
The present invention relates to a magnetic head for perpendicular recording and a method for manufacturing the same, and a magnetic disk storage apparatus mounting the magnetic head for perpendicular recording.
2. Description of the Related Art
In a magnetic disk storage apparatus, the data on a recording medium is read and written by a magnetic head. The areal recording density is required to be increased in order to increase the recording capacity per unit area of the magnetic disk. However, with a current longitudinal recording method, there occurs a problem as follows. As the length of a bit to be recorded decreases, thermal fluctuation of the magnetization of the medium becomes a serious problem which restricts the limit of the areal recording density. There is a perpendicular recording method for recording a magnetization signal in a direction perpendicular to the medium for solving this problem.
There are two types of perpendicular recording methods: a method in which a double layered perpendicular medium having a soft magnetic underlayer is used as a recording medium; and a method in which a single layered perpendicular medium having no underlayer is used. When the double layered perpendicular medium is used as the recording medium, recording is usually performed by using a so-called single pole type head having a main pole and an auxiliary pole.
Further, in order to improve the recording density, the track density and the linear recording density are required to be improved also for perpendicular recording. In order to improve the track density, the track width of the magnetic head is required to be increased in fineness and precision. When perpendicular magnetic recording using the double layered perpendicular medium and the single pole type head is performed, the distribution of the write field generated from the magnetic pole of the single pole type head is largely different from that of the longitudinal magnetic recording. For example, as shown in FIG. 2(A), the contours of the perpendicular component of the write head field intensity are distributed concentrically wherein the maximum intensity occurs from the central portion of the main pole, and exhibit such a distribution that a contour closer to the outside has a more swollen shape. Therefore, the shape of the air bearing surface of the main pole largely affects the recorded magnetization pattern of the medium.
FIG. 2(A) is a distribution diagram of the contours of perpendicular components of head write field in the form of a main pole in the prior art obtained by simulation. FIG. 2(A) indicates that the field distribution is curved toward the trailing side. Herein, the trailing side denotes the downstream side of the disk rotating direction, and it denotes the direction of the arrow indicated as xe2x80x9cdisk rotating direction 17xe2x80x9d in FIG. 2 (A). In contrast, the upstream side of the disk rotating direction is referred to as a leading side. FIG. 2(B) is a diagram showing the magnetization configuration, obtained from simulation, recorded on the medium when a head having such a magnetic field distribution is used. As indicated from FIG. 2(B), the magnetic reversal position in the track central portion is situated more toward the disk rotating direction than in each of the track edge portions, so that the shape of magnetic transition of the medium is curved. Such a phenomenon actually becomes apparent from the observation result by means of a MFM: magnetic force microscopy.
If the shape of magnetic reversal of a medium is curved to the track direction as shown in FIG. 2(B), there occur problems as follows: when reading is carried out by means of a MR/GMR head or the like, the magnetic transition length appears to be large, so that the half-width of an isolated pulse is increased, and at the same time, the recording track width seems to be reduced with an increase in linear recording density. These problems are large hindrances in implementing high density recording.
The present invention provides a magnetic head for perpendicular recording, which is capable of recording a bit in which the degree of curvature of the shape of magnetic transition has been reduced, a manufacturing method thereof, and a magnetic disk storage apparatus mounting the magnetic head for perpendicular recording.
In the present invention, a recess, that is, a hollow is formed on the downstream side of the direction of rotation of the magnetic recording medium, that is, on the trailing side of a main pole of a single pole type head for perpendicular recording.
As for the write field intensity generated from the main pole, the contours thereof are distributed concentrically, wherein the intensity from the central portion of the main pole is maximum. However, it is considered that the shape of recorded magnetic reversal to be recorded on the recording medium is determined by reflecting the shape of the contour at which the write field intensity becomes equal to the coercive force of the recording medium. Therefore, the shape of the air bearing surface of the main pole affects the write field intensity distribution.
As the prior art in which the pole shape of the head has been changed, in Japanese Published Unexamined Patent Application No. Hei 11-213334, there is disclosed a head for in-plane recording in which projections are provided on the leading side of an upper magnetic pole opposed to a common magnetic pole with a gap interposed therebetween, thereby to reduce the expansion of a write field in the track width direction. However, the technology described in Japanese Published Unexamined Patent Application No. Hei 11-213334 is the technology for improving the shape of the write field in the track width direction. Therefore, even if the technology described in Japanese Published Unexamined Patent Application No. Hei 11-213334 is simply converted for perpendicular recording, it is not possible to improve the curvature of the shape of magnetic transition of a medium in the track direction.
The inventors of the present invention have found the following fact. Namely, if the trailing side of the air bearing surface of a main pole is shaped in the form of a recess, it is possible to more linearize the magnetic field distribution whereby the magnetic transition is determined. By using a single pole type head having such a main pole shape, it is possible to reduce the degree of curvature of the shape of magnetic transition. In consequence, it is possible to reduce the following problems: when reading is performed by means of a reading head, the magnetic transition length appears to be large, so that the half-width of an isolated pulse seems to be reduced, and at the same time, the recording track width is narrowed with an increase in linear recording density. Further, it is possible to provide a magnetic disk storage apparatus having a more improved track density than ever by mounting such a single pole type head therein.